The glycosyltransferases are a family of intracellular membrane-bound enxymes that participate in the coordinate assembly of the carbohydrate moiety of glycoporteins and glycolipids. The localization of glycosyltransferases on the cell surface and their role in intercellular adhesion and contact inhibition have been postulated. The important biosynthetic role of the intracellular glycosyltransferases is well documented. In direct contract, the existence of plasma-membrane localized glycosyltransferases, the chemical nature of these putative enzymes, their relationship to their intracellular counterparts, and their role in intercellular adhesion is either a subject of controversy or has not been established. We have recently produced and characterized an antiserum against a specific bovine transferase, UDP-galactose:N-acetylglucosamine galactosyltransferase (GT), using a soluble form of the enzyme as the antigen after affinity-purification. This antiserum is cross-reactive with GR from several mammalian species including rat, mouse and man. This cross-reactivity has formed the experimental basis for the development of a sensitive and highly specific RIA for the GT. This antiseru, to the best of our knowledge, is th efirst high titer, cross-reactive antiserum that have been developed against a specific glycosyltransferase. Using this antiserum we have directly demonstrated the existence of a cell surface GT (ecto-GT) in a variety of different cell types and are now in a unique position to directly probe the structure and biological significance of this ecto-transferase. Using this highly specific immunological probe for GT we plan: (1) to partially chemical characterize the ecto-GT, (2) to probe the structural organization of the ecto-GT by a combination of chemical and electron microscopic techniques, (3) to determine if the ecto-GT is structurally related to the intracellular Golgi-membrane GT, (4) to quantiate and determine the topological distribution of the ecto-GT from on cells and their transformed variants, and (5) to determine the role o the ecto-GT in intercellular adhesion using a human lung derived tissue culture system in which individual cells form free-floating multi-cellular aggregates.